Beryllium From Wikipedia, the free encyclopedia This is a good article. Click here for more information. Beryllium 4Be - ↑ Be ↓ Mg lithium ← beryllium → boron Beryllium in the periodic table Appearance white-gray metallic General properties Name, symbol, number beryllium, Be, 4 Pronunciation /bəˈrɪliəm/ bə-ril-ee-əm Element category alkaline earth metal Group, period, block 2 (alkaline earth metals), 2, s Standard atomic weight 9.0121831(5) Electron configuration [He] 2s2 2, 2 Physical properties Phase solid Density (near r.t.) 1.85 g·cm−3 Liquid density at m.p. 1.690 g·cm−3 Melting point 1560 K, 1287 °C, 2349 °F Boiling point 3243 K, 2970 °C, 5338 °F Critical point (extrapolated) 5205 K, MPa Heat of fusion 12.2 kJ·mol−1 Heat of vaporization 292 kJ·mol−1 Molar heat capacity 16.443 J·mol−1·K−1 Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1462 1608 1791 2023 2327 2742 Atomic properties Oxidation states 2, 1[1] (amphoteric oxide) Electronegativity 1.57 (Pauling scale) Ionization energies (more) 1st: 899.5 kJ·mol−1 2nd: 1757.1 kJ·mol−1 3rd: 14848.7 kJ·mol−1 Atomic radius 112 pm Covalent radius 96±3 pm Van der Waals radius 153 pm Miscellanea Crystal structure hexagonal close-packed Beryllium has a hexagonal close packed crystal structure Magnetic ordering diamagnetic Electrical resistivity (20 °C) 36 nΩ·m Thermal conductivity 200 W·m−1·K−1 Thermal expansion (25 °C) 11.3 µm·m−1·K−1 Speed of sound (thin rod) (r.t.) 12890[2] m·s−1 Young's modulus 287 GPa Shear modulus 132 GPa Bulk modulus 130 GPa Poisson ratio 0.032 Mohs hardness 5.5 Vickers hardness 1670 MPa Brinell hardness 600 MPa CAS registry number 7440-41-7 History Discovery Louis Nicolas Vauquelin (1797) First isolation Friedrich Wöhler & Antoine Bussy (1828) Most stable isotopes Main article: Isotopes of beryllium iso NA half-life DM DE (MeV) DP 7Be trace 53.12 d ε 0.862 7Li γ 0.477 - 9Be 100% 9Be is stable with 5 neutrons 10Be trace 1.36×106 y β− 0.556 10B v t e · references Beryllium is the chemical element with the symbol Be and atomic number 4. Because any beryllium synthesized in stars is short-lived, it is a relatively rare element in the universe. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. As a free element it is a steel-gray, strong, lightweight and brittle alkaline earth metal. Beryllium improves many physical properties when added as an alloying element to aluminium, copper (notably the alloy beryllium copper), iron and nickel.[3] Tools made of beryllium copper alloys are strong and hard and do not create sparks when they strike a steel surface. In structural applications, the combination of high flexural rigidity, thermal stability, thermal conductivity and low density (1.85 times that of water) make beryllium metal a desirable aerospace material for aircraft components, missiles, spacecraft, and satellites.[3] Because of its low density and atomic mass, beryllium is relatively transparent to X-rays and other forms of ionizing radiation; therefore, it is the most common window material for X-ray equipment and components of particle physics experiments.[3] The high thermal conductivities of beryllium and beryllium oxide have led to their use in thermal management applications. The commercial use of beryllium requires the use of appropriate dust control equipment and industrial controls at all times because of the toxicity of inhaled beryllium-containing dusts that can cause a chronic life-threatening allergic disease called berylliosis in some people.[4] Contents [hide] 1 Characteristics 1.1 Physical properties 1.2 Nuclear properties 1.3 Isotopes and nucleosynthesis 1.4 Occurrence 2 Production 3 Chemical properties 4 History 4.1 Etymology 5 Applications 5.1 Radiation windows 5.2 Mechanical applications 5.3 Mirrors 5.4 Magnetic applications 5.5 Nuclear applications 5.6 Acoustics 5.7 Electronic 6 Precautions 7 See also 8 Notes 9 References 10 Further reading 11 External links Characteristics[edit] Physical properties[edit] Beryllium is a steel gray and hard metal that is brittle at room temperature and has a close-packed hexagonal crystal structure.[3] It has exceptional stiffness (Young's modulus 287 GPa) and a reasonably high melting point. The modulus of elasticity of beryllium is approximately 50% greater than that of steel. The combination of this modulus and a relatively low density results in an unusually fast sound conduction speed in beryllium – about 12.9 km/s at ambient conditions. Other significant properties are high specific heat (1925 J·kg−1·K−1) and thermal conductivity (216 W·m−1·K−1), which make beryllium the metal with the best heat dissipation characteristics per unit weight. In combination with the relatively low coefficient of linear thermal expansion (11.4×10−6 K−1), these characteristics result in a unique stability under conditions of thermal loading.[5] Nuclear properties[edit] Natural beryllium, save for slight contamination by cosmogenic radioisotopes, is essentially beryllium-9, which has a nuclear spin of 3/2-. Beryllium has a large scattering cross section for high-energy neutrons, about 6 barns for energies above approximately 10 KeV. Therefore, it works as a neutron reflector and neutron moderator, effectively slowing the neutrons to the thermal energy range of below 0.03 eV, where the total cross section is at least an order of magnitude lower – exact value strongly depends on the purity and size of the crystallites in the material. The single primordial beryllium isotope 9Be also undergoes a (n,2n) neutron reaction with neutron energies over about 1.9 MeV, to produce 8Be, which almost immediately breaks into two alpha particles. Thus, for high-energy neutrons beryllium is a neutron multiplier, releasing more neutrons than it absorbs. This nuclear reaction is:[6] 9 4Be + n → 2(4 2He) + 2n Neutrons are liberated when beryllium nuclei are struck by energetic alpha particles[5] producing the nuclear reaction 9 4Be + 4 2He → 12 6C + n , where 4 2He is an alpha particle and 12 6C is a carbon-12 nucleus.[6] Beryllium also releases neutrons under bombardment by gamma rays. Thus, natural beryllium bombarded either by alphas or gammas from a suitable radioisotope is a key component of most radioisotope-powered nuclear reaction neutron sources for the laboratory production of free neutrons. As a metal, beryllium is transparent to most wavelengths of X-rays and gamma rays, making it useful for the output windows of X-ray tubes and other such apparatus. Isotopes and nucleosynthesis[edit] Main articles: Isotopes of beryllium and beryllium-10 Both stable and unstable isotopes of beryllium are created in stars, but these do not last long. It is believed that most of the stable beryllium in the universe was originally created in the interstellar med